The present invention relates to a thin magnetic tape with good tracking and very little output variation in VTRs. More particularly, the present invention relates to a magnetic tape in which there is little meandering of the tape edge trajectory and the ratio of the intensity of short cycle meandering components is low.
Generally, magnetic tapes with prescribed width are manufactured by first forming a magnetic layer on a wide flexible support, forming a backcoat layer on the reverse side thereof, and then using a slitter to slit to prescribed width. That is, first, a ferromagnetic powder is mixed with and dispersed in binder, additives, an organic solvent, and the like to prepare a coating material for forming magnetic layers. This coating material is then applied on one surface of a wide flexible support, magnetically oriented, and dried to form a magnetic layer. A coating material for forming backcoat layers is prepared by admixing and dispersing abrasives, binder, additives, an organic solvent, and the like, and this coating material is applied to the reverse side of the flexible support and dried to form a backcoat layer. The wide magnetic tape blank that has been thus manufactured is processed by calendering or the like and slitted to desired width, such as 8 mm, xc2xd inch, or one inch, are formed therefrom with a slitter to manufacture magnetic tape.
The usual system is one in which the magnetic tape blank is placed on a slitter configured of multiple opposed upper blade and lower blade and slit to desired width, and each of the magnetic tapes with prescribed width that is obtained is passed over guide rollers and wound onto a hub. In the slitted magnetic tape, the tape edge trajectory traced by each of the two edges in the width direction of the magnetic tape (referred to hereinafter as xe2x80x9ctape edge trajectoryxe2x80x9d) is desirably linear when observed in a direction perpendicular to the magnetic layer surface. However, since there is eccentricity and vibration in the rollers and slitting blades from which the slitter is composed, variation in tension and eccentricity in the winding shafts, and transverse shifting of the magnetic tape blank, there is meandering of the tape edge trajectory of the magnetic tape that is actually manufactured.
In recent years, digitization of data has led to a massive increase in the amount of information that is recorded. As a result, magnetic tapes and VTRs have been improved in various ways. In magnetic tapes, microgranular magnetic powder of short major axis length has been employed and the thickness of the magnetic tape itself has been reduced to increase the recording capacity per unit volume. In VTRs, the wavelength has been shortened and the track narrowed to increase the recording capacity per unit volume. Combining these magnetic tapes and VTRs permits a substantial increase in volume recording density.
In such thin tapes for high density recording, the above-described slitting method is employed to slit in the manufacturing of tapes having meandering tape edge trajectories similar to those of conventional thick tapes. However, the thin tapes differ from conventional thick tapes in that stiffness, particularly in the width direction, is low and tape strength is low. Thus, there is a problem in that when position regulation by the upper and lower flanges of the guide rollers in the VTR is performed poorly when running a thin tape through a VTR, leading to tracking failure, variation in output increases. This problem is particularly marked in thin tapes with a width direction stiffness equal to or less than 70 mg.mm2.
One method of solving this problem is to improve position regulation by the guide rollers and thus improve tracking. However, when position regulation is improved, since the strength of the magnetic tape in the width direction is low as set forth above, the edges thereof buckle and crease, which ends up causing xe2x80x9cedge creasesxe2x80x9d resulting in dropout.
Accordingly, an object of the present invention is to provide a thin magnetic tape for high-density recording affording good tracking and extremely low output variation. That is, an object of the present invention is to provide a thin magnetic tape in which meandering of the tape edge trajectories is controlled to permit linear running in a VTR.